Abstract: Disclosure is made of a bar-clamping device having a hollow spindle carrying first and second collets, each provided with a closing drive ensuring independent axial motion of one of the collets relative to the other. The closing drives of each collet are installed in the spindle and designed so that the axial efforts produced during clamping of a bar are directed in the opposite directions.

Abstract: An apparatus for electroerosive piercing of holes in workpieces having an electrode tool in the form of a rod placed with a clearance in a shell and projecting therefrom, a device for feeding and rotating the rod mechanically connected to a device for reciprocating the shell relative to the rod. The device for reciprocating the shell relative to the rod is fashioned as a hydraulic cylinder, a piston of which has the shell rigidly secured thereto at the side of the workpiece, and at least one cavity of the hydrauylic cylinder is connected to a system for feeding and discharging a working fluid, the piston having at least one passage communicable with the interior of the shell of the electrode tool and wherethrough the rod of the electrode tool extends with a clearance.

Abstract: A device for electrical discharge piercing of holes in components comprises a tool electrode mounted in an electrode holder (18) and made as a rod (26) enclosed, with a clearance, in a sheath (27) and somewhat projecting therefrom, and a contrivance for traversing, locking and wear compensation of the tool electrode.